BACKGROUND OF THE INVENTION
1. Field of the Invention:
[0001] This invention relates to a method and apparatus for the production of a cast article
having a small hole. More particularly, this invention relates to a metal mold casting
technique, particularly to a small hole forming technique usable in the production
of a molded article having a small hole by metal mold casting of an amorphous alloy
(metal glass), particularly an optical connector parts such as a ferrule and a capillary.
2. Description of the Prior Art:
[0002] As a typical example of a molded article which has a small hole and which requires
high dimensional accuracy, a ferrule or capillary of an optical connector may be cited.
[0003] Now referring to the attached drawings for explanation, Fig. 1 illustrates one mode
of the optical connector ferrule 10 of a one-piece construction comprising a capillary
part 11 and a flange part 12. Specifically, this ferrule 10 is composed of the capillary
part 11 which has formed along the axis thereof a through-hole 13 of a small diameter
intended for the insertion of an optical fiber 17 (or the basic thread of an optical
fiber coated with a plastic thin film) and the flange part 12 which has formed along
the axis thereof a through-hole 14 of a large diameter intended for the insertion
of a sheathed optical fiber 16 (the optical fiber coated with a sheath). The through-hole
13 of the small diameter and the through-hole 14 of the large diameter are connected
into each other through a tapered part 15. The connection of a pair of optical fibers
17, 17 is attained by inserting into a split sleeve 18 through the opposite ends thereof
the ferrules 10, 10 having the optical fibers already inserted and joined therein
and then abutting the end parts of the ferrules 10, 10. As a result, the optical fibers
17, 17 are allowed to have their leading ends abutted and joined in a state having
the axes thereof aligned to each other.
[0004] Fig. 2 illustrates another mode of the optical connector ferrule 10a comprising a
capillary part 11a and a flange part 12a as separate components.
[0005] The diameter of the small hole into which the optical fiber is inserted depends on
the type of ferrule. For instance, the capillary (ferrule) of the SC type has a small
hole of 0.126 mm in diameter and 10 mm in length.
[0006] Heretofore, the ferrules are manufactured by using ceramics such as zirconia. The
formation of a small hole in the ferrule is attained by preparatorily forming a ceramic
ferrule blank having a relatively smaller hole by injection molding, calcining the
ceramic ferrule blank, and then subjecting the calcined ceramic ferrule blank to wire
lapping thereby finishing it to a specified dimension. Furthermore, the production
of the ceramic ferrule comprises, besides the above inside diameter finishing, many
steps of machining such as abrasive finishing of the outside diameter and polishing
of the leading end into the spherical convex surface (PC polishing). Accordingly,
the process of production is lengthy and the cost of production is inevitably large.
[0007] As a method capable of solving the problems mentioned above, the assignee of this
application has proposed a method which, by the combination of the conventional technique
based on the metal mold casing method with an amorphous alloy exhibiting a glass transition
region, allows an amorphous alloy molded article satisfying a predetermined shape,
dimensional accuracy, and surface quality to be mass-produced with high efficiency
by a single process, even when the article is that having a small hole such as an
optical connector ferrule or an article having a complicated shape (Japanese Patent
Application, KOKAI (Early Publication) No. 10-186176). In the method for the production
of the amorphous alloy molded article having a small hole disclosed in this patent
literature, basically the formation of the small hole is effected by injecting a melt
of a material capable of producing an amorphous alloy into a mold cavity having a
core pin set therein at a high speed and thereafter the core pin is drawn from the
resultant cast product to form a small hole.
SUMMARY OF THE INVENTION
[0008] To manufacture a cast article having a small hole, usually a core pin uniformly coated
with a release agent should be used. Since the release agent used evaporates rapidly
when the molten metal contacts the core pin, however, bubbles or blemishes remain
in the cast article. Furthermore, the direction of evaporation of the release agent
can not be uniformly and constantly controlled, which poses the problem that the dimensional
accuracy of the small hole portion can not be heightened to a desired level. Conversely,
when the injection pressure during the casting is increased to obtain the cast article
with high accuracy, other problems will be incurred that the core pin can not be drawn
out from the cast product because any gap will not remain between the cast material
and the core pin for forming the small hole. Further, this process has the problem
of exposing the core pin to the possibility of sustaining scarring in its surface
or even breakage during the casting or during the operation of drawing of the core
pin after casting. Since the core pin is made of a sintered hard metal or cemented
carbide and thus expensive, the fact that the scarred or broken core pin can not be
used repeatedly forms a large factor for boosting the production cost of the article.
[0009] Such problems are not particular to the optical connector ferrule or capillary, but
common to the metal mold casting of a metal molded article having a small hole.
[0010] It is, therefore, a fundamental object of the present invention to provide a method
and apparatus capable of producing a cast article having a small hole at low cost
with high productivity in a short time, which can diminish various problems caused
by the difficulty of drawing of a core pin from the cast product after the casting
or the durability of the core pin as mentioned above.
[0011] A further particular object of the present invention is to provide a method and apparatus
which allow a molded article satisfying a predetermined shape, dimensional accuracy,
and surface quality to be molded by a simple process even when the article is an amorphous
alloy molded article having a slender hole and, therefore, enable to provide an inexpensive
amorphous alloy molded article having a small hole and excelling in the durability,
mechanical strength, resistance to impact and the like, particularly an optical connector
part such as a ferrule or capillary.
[0012] To accomplish the object mentioned above, the first aspect of the present invention
provides a method for the production of a cast article having a small hole.
[0013] The first embodiment of the method according to the present invention is characterized
by the fact that in the casting of a molten metal into a cavity of a metal mold having
a linear core member of a desired cross-sectional shape preparatorily set therein
to produce a cast product, a linear core member having a surface film formed by surface
coating or by subjecting to a surface treatment is used as the linear core member,
and the linear core member is drawn out from the cast product after the casting, thereby
forming in the cast product a small hole of the cross-sectional shape substantially
equal to that of the linear core member. In this case, the preferred mode is constructed
so that a part or the whole of the surface film is peeled off the surface of the linear
core member upon drawing it from the cast product after the casting, thereby enabling
the linear core member to be drawn from the inside of the cast product.
[0014] The second embodiment of the method of the present invention is characterized by
the fact that in the method comprising injecting a molten metal into a cavity of a
metal mold having a linear core member of a desired cross-sectional shape preparatorily
set therein to produce a cast product and drawing out the linear core member from
the cast product to form a small hole having the cross-sectional shape of the linear
core member, the linear core member is so constructed as to elastically deform in
the drawing direction to have a diameter smaller than the original diameter upon drawing
the linear core member from the cast product after the casting, thereby enabling the
linear core member to be drawn from the inside of the cast product.
[0015] The second aspect of the present invention provides an apparatus for the production
of a cast article having a small hole characterized by comprising a metal mold provided
with a cavity which defines the outer shape of an article, a movable cylindrical guide
member having a center bore and disposed in the mold slidably so as to project into
and draw back from the cavity, and a linear core member to be set in the mold via
the center bore of the cylindrical guide member, and preferably further means for
applying a tension load, preferably not more than 1960 N/mm
2, to the linear core member in its longitudinal direction.
[0016] By using the method and apparatus mentioned above, it is possible to manufacture
a cast article having a small hole, particularly an amorphous alloy moled article,
more particularly an optical connector ferrule or capillary, with high productivity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Other objects, features, and advantages of the invention will become apparent from
the following description taken together with the drawings, in which:
Fig. 1 is a fragmentary cross-sectional view schematically illustrating an optical
connector ferrule of a one-piece construction comprising a capillary part and a flange
part;
Fig. 2 is a fragmentary cross-sectional view schematically illustrating another optical
connector ferrule comprising a capillary part and a flange part as separate components;
Figs. 3A to 3C are fragmentary cross-sectional views schematically illustrating an
embodiment of the steps of production of a cast article according to the present invention;
Fig. 4 is a fragmentary cross-sectional view schematically illustrating another embodiment
of the method according to the present invention using a linear core member coated
with a surface film;
Fig. 5 is a fragmentary cross-sectional view schematically illustrating still another
embodiment of the method according to the present invention using a linear core member
made of a material easily susceptible of elastic deformation;
Fig. 6 is a fragmentary cross-sectional view schematically illustrating another embodiment
of an apparatus for the production of a cast article according to the present invention;
and
Fig. 7 is a cross-sectional view schematically illustrating a molded article produced
by using the apparatus shown in Fig. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] In view of the problems caused by the difficulty of drawing of a linear core member
from a cast product after the casting or by the durability of the linear core member
as mentioned above, the method for the production of the cast article according to
the present invention improves the drawing characteristics of the linear core member.
The following methods may be cited as the methods for improving the drawing characteristics
of the linear core member after the casting. In the following description, the linear
core member is referred to as "wire".
(1) Method for subjecting the wire to surface coating or surface treatment
[0019] This method is to coat the surface of the wire with a easily peelable film or to
utilize the wire having a surface film inevitably formed during the production thereof
so that the wire as the linear core member tends to be easily separated from the cast
product. By this method, when the wire is drawn from the cast product, the surface
film is partly or as a whole peeled off the wire because the surface film of the wire
is closely attached to the cast product and, therefore, only the wire is separated
from the cast product. As a result, a small hole having the cross-sectional shape
of the wire is formed in the cast article.
[0020] The surface film of the wire mentioned above may be formed by a method of depositing
a material, such as oxides, nitrides, and carbides, on the surface of the wire as
by a physical vapor deposition process (PVD) and a chemical vapor deposition process
(CVD), or by other suitable method such as electroplating, electroless plating, and
hot dipping of metal. When the wire is made of an active metallic material, the wire
having a film of oxides, nitrides, or carbides containing a component element of the
wire remained as a scale may be utilized as it is, without the need of a specific
treatment in the production process. The film thickness is desired to be in the range
of about 0.5 µm to about 100 µm in terms of the peelable characteristics of the film
and the drawing characteristics of the wire. In this method, various materials can
be used as the wire material. Among the other wire materials, the Ti-based alloys
having excellent heat resistance prove to be particularly advantageous.
(2) Method using an elastic wire or a superelastic wire
[0021] This method is to utilize a wire having a high elastic limit as the wire (linear
core member). By using such a wire, the wire is elastically deformed in the drawing
direction when it is drawn from the cast product and thus its diameter becomes small
relative to a small hole to be formed in the cast product. As a result, the wire can
be drawn from the cast product because a clearance can be secured between the wire
and the cast product, and the small hole having the cross-sectional shape of the wire
is formed in the cast molded article. As the wire mentioned above, a material for
spring, a high tensile strength steel, and a superelastic material (Ni-Ti superelastic
alloys etc.), for example, may be used.
[0022] Incidentally, the aforementioned methods (1) and (2) may be employed in combination.
[0023] According to the present invention, in order to protect the wire (linear core member)
when it is set in the cavity of a metal mold or during the casting process, it is
possible to use a metal mold provided with a movable cylindrical guide member which
is disposed in the mold slidably so as to project into and draw back from the cavity.
When the wire is set in the cavity of the mold together with the cylindrical guide
member by inserting it through a center bore of the guide member, a tension load of
a desired level, preferably not more than about 1960 N/mm
2, is applied to the wire in its longitudinal direction. By using such a cylindrical
guide member, a part of the wire covered with the guide member is protected from the
contact with the molten metal and the surface area of the wire being in contact with
the cast product becomes small. As a result, the proportion of the scarring or breakage
of the wire during the drawing step decreases. Moreover, since a tension load is applied
to the wire, the incidental bending of the wire during the injection of the molten
metal into the cavity of the mold is prevented. Accordingly, it is possible to manufacture
a cast article having a small hole with high accuracy. Incidentally, this method can
be employed in combination with either or both of the methods mentioned above.
[0024] The size of the wire may be arbitrarily varied depending on the desired diameter
of the small hole. In the case of optical connector parts, the size of the wire is
set in the range of 0.025 mm to 1 mm in diameter.
[0025] Although the casting material used in the method of the present invention does not
need to be limited to any particular substance but may be any of the materials which
can be used in the conventional casting method, a substantially amorphous alloy containing
an amorphous phase in a volumetric ratio of at least 50% can be advantageously used.
Among other amorphous alloys answering this description, the amorphous alloy having
a composition represented by either one of the following general formulas (1) to (6)
can be more advantageously used.
M
1aM
2bLn
cM
3dM
4eM
5f (1)
wherein M
1 represents either or both of the two elements, Zr and Hf; M
2 represents at least one element selected from the group consisting of Ni, Cu, Fe,
Co, Mn, Nb, Ti, V, Cr, Zn, Al, and Ga; Ln represents at least one element selected
from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm (mish metal:
aggregate of rare earth elements); M
3 represents at least one element selected from the group consisting of Be, B, C, N,
and O; M
4 represents at least one element selected from the group consisting of Ta, W, and
Mo; M
5 represents at least one element selected from the group consisting of Au, Pt, Pd,
and Ag; and a, b, c, d, e, and f represent such atomic percentages as respectively
satisfy 25 ≦ a ≦ 85, 15 ≦ b ≦ 75, 0 ≦ c ≦ 30, 0 ≦ d ≦ 30, 0 ≦ e ≦ 15, and 0 ≦ f ≦
15.
[0026] The above amorphous alloy includes those represented by the following general formulas
(1-a) to (1-p).
M
1aM
2b (1-a)
[0027] This amorphous alloy has large negative enthalpy of mixing and good producibility
of the amorphous structure due to the coexistence of the M
2 element and Zr or Hf.
M
1aM
2bLn
c (1-b)
[0028] The addition of a rare earth element to the alloy represented by the above general
formula (1-a), as in this amorphous alloy, enhances the thermal stability of the amorphous
structure.
M
1aM
2bM
3d (1-c)
M
1aM
2bLn
cM
3d (1-d)
[0029] The filling of gaps in the amorphous structure with the M
3 element having a small atomic radius (Be, B, C, N, or O), as in these amorphous alloys,
makes the structure stable and enhances the producibility of the amorphous structure.
M
1aM
2bM
4e (1-e)
M
1aM
2bLn
cM
4e (1-f)
M
1aM
2bM
3dM
4e (1-g)
M
1aM
2bLn
cM
3dM
4e (1-h)
[0030] The addition of a high melting metal, M
4 (Ta, W, or Mo) to the above alloys, as in these amorphous alloys, enhances the heat
resistance and corrosion resistance without affecting the producibility of the amorphous
structure.
M
1aM
2bM
5f (1-i)
M
1aM
2bLn
cM
5f (1-j)
M
1aM
2bM
3dM
5f (1-k)
M
1aM
2bLn
cM
3dM
5f (1-l
M
1aM
2bM
4eM
5f (1-m)
M
1aM
2bLn
cM
4eM
5f (1-n)
M
1aM
2bM
3dM
4eM
5f (1-o)
M
1aM
2bLn
cM
3dM
4eM
5f (1-p)
[0031] These amorphous alloys containing a noble metal, M
5 (Au, Pt, Pd, or Ag) will not be brittle even if the crystallization occurs.
Al
100-g-h-iLn
gM
6hM
3i (2)
wherein Ln represents at least one element selected from the group consisting of Y,
La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm; M
6 represents at least one element selected from the group consisting of Ti, V, Cr,
Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W; M
3 represents at least one element selected from the group consisting of Be, B, C, N,
and O; and g, h, and i represent such atomic percentages as respectively satisfy 30
≦ g ≦ 90, 0 < h ≦ 55, and 0 ≦ i ≦ 10.
[0032] The above amorphous alloy includes those represented by the following general formulas
(2-a) and (2-b).
Al
100-g-hLn
gM
6h (2-a)
[0033] This amorphous alloy has large negative enthalpy of mixing and good producibility
of the amorphous structure.
Al
100-g-h-iLn
gM
6hM
3i (2-b)
[0034] This amorphous alloy has a stable structure and enhanced producibility of the amorphous
structure due to the filling of gaps in the amorphous structure with the M
3 element having a small atomic radius (Be, B, C, N, or O).
Mg
100-pM
7p (3)
wherein M
7 represents at least one element selected from the group consisting of Cu, Ni, Sn,
and Zn; and p represents an atomic percentage falling in the range of 5 ≦ p ≦ 60.
[0035] This amorphous alloy has large negative enthalpy of mixing and good producibility
of the amorphous structure.
Mg
100-q-rM
7qM
8r (4)
wherein M
7 represents at least one element selected from the group consisting of Cu, Ni, Sn,
and Zn; M
8 represents at least one element selected from the group consisting of Al, Si, and
Ca; and q and r represent such atomic percentages as respectively satisfy 1 ≦ q ≦
35 and 1 ≦ r ≦ 25.
[0036] The filling of gaps in the amorphous structure of the alloy of the above general
formula (3) with the M
8 element having a small atomic radius (Al, Si, or Ca), as in this amorphous alloy,
makes the structure stable and enhances the producibility of the amorphous structure.
Mg
100-q-sM
7qM
9s (5)
Mg
100-q-r-sM
7qM
8rM
9s (6)
wherein M
7 represents at least one element selected from the group consisting of Cu, Ni, Sn,
and Zn; M
8 represents at least one element selected from the group consisting of Al, Si, and
Ca; M
9 represents at least one element selected from the group consisting of Y, La, Ce,
Nd, Sm, and Mm; and q, r, and s represent such atomic percentages as respectively
satisfy 1 ≦ q ≦ 35, 1 ≦ r ≦ 25, and 3 ≦ s ≦ 25.
[0037] The addition of a rare earth element to the alloy of the general formula (3) or (4)
mentioned above, as in these amorphous alloys, enhances the thermal stability of the
amorphous structure.
[0038] Among other amorphous alloys mentioned above, the Zr-TM-Al and Hf-TM-Al (TM: transition
metal) amorphous alloys having very wide differences between the glass transition
temperature (Tg) and the crystallization temperature (Tx) exhibit high strength and
high corrosion resistance, possess wide supercooled liquid ranges (glass transition
ranges),

, of not less than 30 K, and extremely wide supercooled liquid ranges of not less
than 60 K in the case of the Zr-TM-Al amorphous alloys. In the above temperature ranges,
these amorphous alloys manifest very satisfactory workability owing to viscous flow
even at such low stress not more than some tens MPa. They are characterized by being
produced easily and very stably as evinced by the fact that they are enabled to furnish
an amorphous bulk material even by a casting method using a cooling rate of the order
of some tens K/s. By the molding process utilizing the viscous flow resorting to the
glass transition range as well, these alloys produce amorphous materials and permit
very faithful reproduction of the shape and size of a molding cavity of a metal mold.
[0039] The Zr-TM-Al and Hf-TM-Al amorphous alloys to be used in the present invention possess
very large range of ΔTx, though variable with the composition of alloy and the method
of determination. The Zr
60Al
15Co
2.5Ni
7.5Cu
15 alloy (Tg: 652K, Tx: 768K), for example, has such an extremely wide Δ Tx as 116 K.
It also offers very satisfactory resistance to oxidation such that it is hardly oxidized
even when it is heated in the air up to the high temperature of Tg. The Vickers hardness
(Hv) of this alloy at temperatures from room temperature through the neighborhood
of Tg is up to 460 (DPN), the tensile strength thereof is up to 1,600 MPa, and the
bending strength thereof is up to 3,000 MPa. The thermal expansion coefficient, α
of this alloy from room temperature through the neighborhood of Tg is as small as
1 x 10
-5/K, the Young's modulus thereof is 91 GPa, and the elastic limit thereof in a compressed
state exceeds 4 - 5%. Further, the toughness of the alloy is high such that the Charpy
impact value falls in the range of 60 - 70 kJ/m
2. This alloy, while exhibiting such properties of very high strength as mentioned
above, has the flow stress thereof lowered to the neighborhood of 10 MPa when it is
heated up to the glass transition range thereof. This alloy, therefore, is characterized
by being worked very easily and being manufactured with low stress into minute parts
and high-precision parts complicated in shape. Moreover, owing to the properties of
the so-called glass (amorphous) substance, this alloy is characterized by allowing
manufacture of formed (deformed) articles with surfaces of extremely high smoothness
and having substantially no possibility of forming a step which would arise when a
slip band appeared on the surface as during the deformation of a crystalline alloy.
[0040] Generally, an amorphous alloy begins to crystallize when it is heated to the glass
transition range thereof and retained therein for a long time. In contrast, the aforementioned
alloys which possess such a wide Δ Tx range as mentioned above enjoy a stable amorphous
phase and, when kept at a temperature properly selected in the Δ Tx range, avoid producing
any crystal for a duration up to about two hours. The user of these alloys, therefore,
does not need to feel any anxiety about the occurrence of crystallization during the
standard molding process.
[0041] The aforementioned alloys manifest these properties unreservedly during the course
of transformation thereof from the molten state to the solid state. Generally, the
manufacture of an amorphous alloy requires rapid cooling. In contrast, the aforementioned
alloys allow easy production of a bulk material of a single amorphous phase from a
melt by the cooling which is effected at a rate of about 10 K/sec. The solid bulk
material consequently formed also has a very smooth surface. The alloys have transferability
such that even a scratch of the order of microns inflicted by the polishing work on
the surface of a metal mold is faithfully reproduced.
[0042] When the aforementioned alloys are adopted as the casting material, therefore, the
metal mold to be used for producing the molded article is only required to have the
surface thereof adjusted to fulfill the surface quality expected of the molded article
because the cast product faithfully reproduces the surface quality of the metal mold.
In the conventional metal mold casting method, therefore, these alloys allow the steps
for adjusting the size and the surface roughness of the molded article to be omitted
or diminished.
[0043] The characteristics of the aforementioned amorphous alloys including in combination
relatively low hardness, high tensile strength, high bending strength, relatively
low Young's modulus, high elastic limit, high impact resistance, high resistance to
abrasion, smoothness of surface, and highly accurate castability or workability render
these alloys appropriate for use as the material for the molded articles used in various
fields such as, for example, a ferrule or a sleeve for the optical connector. Furthermore,
an amorphous alloy possesses highly accurate castability and machinability as well
as excellent transferability capable of faithfully reproducing the contour of the
cavity of the mold. It is, therefore, possible to manufacture the molded article satisfying
dimensional prescription, dimensional accuracy, and surface quality by the metal mold
casting method or molding method with high mass productivity by a single process insofar
as the metal mold to be used is suitably prepared. The excellent transferability of
the amorphous alloy capable of faithfully reproducing the contour of the cavity of
the mold, however, means that there is little gap between the surface of the cavity
of the mold and the cast product. This fact, therefore, poses the problem that the
core pin is injured or broken when the cast product is extracted from the mold, because
the core pin used for forming a small hole is so slender as to have insufficient strength,
as mentioned above. Since the present invention solves this problem, it is particularly
advantageously applicable to the production of the amorphous alloy molded article
having a small hole.
[0044] As a metallic material used for the production of the cast article according to the
present invention, alloys for die casting such as Al-based alloys, Mg-based alloys,
Zn-based alloys, Fe-based alloys, Cu-based alloys, titanium alloys and the like may
be advantageously used besides amorphous alloys mentioned above. Such alloys for die
casting are used in the conventional casting process and inexpensive in comparison
with ceramics and amorphous alloys commonly used for the production of the optical
connector parts. By using such alloys for die casting, the optical connector parts
may be easily produced by molding the alloy under pressure in a metal mold by means
of a die casting machine.
[0045] As Al-based alloys, Al-Si, Al-Mg, Al-Si-Cu, or Al-Si-Mg aluminum alloys for die casting
such as, for example, ADC1, ADC5, and ADC12 according to JIS (Japanese Industrial
Standard) class symbol may be advantageously used. Among other alloys mentioned above,
ADC12 proves to be particularly advantageous. Likewise, as Mg-based alloys, Mg-Al
or Mg-Al-Zn magnesium alloys for die casting such as, for example, MDC1A, MDC2A, and
MDC3A may be advantageously used. Among other alloys mentioned above, MDC1A proves
to be particularly advantageous. As Zn-based alloys, Zn-Al, Zn-Al-Cu, Zn-Al-Cu-Mg,
or Zn-Mn-Cu zinc alloys for die casting such as, for example, AG40A, AG41A, and high
Mn alloys may be advantageously used. Among other alloys mentioned above, high Mn
alloys prove to be particularly advantageous. As Fe-based alloys, gray cast iron,
austenite cast iron, and stainless cast steel, for example, may be cited. Among other
alloys mentioned above, stainless cast steel proves to be particularly advantageous.
As Cu-based alloys, brass, bronze, and aluminum bronze, for example, may be cited.
Among other alloys mentioned above, aluminum bronze proves to be particularly advantageous.
Typical examples of titanium alloys include α type alloys, β type alloys, and α +
β type alloys. Among other alloys mentioned above, α + β type alloys prove to be particularly
advantageous.
[0046] Among other alloys enumerated above, Fe-M-X alloys represented by the following general
formula prove to be particularly advantageous.
Fe
xM
yX
z
wherein M represents Ni and/or Co, X represents at least one element selected from
the group consisting of Mn, Si, Ti, Al, and C, and x, y, and z stand for weight percentages
in the ranges of 30 ≦ y ≦ 40, 0 ≦ z ≦ 10, x being the balance inclusive of unavoidable
impurities. Since the Fe-M-X alloys represented by the above general formula permit
easy machining with high dimensional accuracy and have a coefficient of linear thermal
expansion approximating to that of an optical fiber, they are suitable as the material
for ferrules into which the optical fiber is fixed.
[0047] Then, some embodiments according to the present invention will be described more
concretely below with reference to the drawings.
[0048] Fig. 3A illustrates the schematic construction of one mode of embodying a method
and apparatus for the production of the cast article having a small hole according
to the present invention. In the figures, 3A and 3B, reference numeral 1 denotes a
split metal mold provided with a cavity 2 adapted to define the outside dimension
of a product, and 3 denotes an elongated wire (linear core member) subjected to surface
coating or surface treatment or a wire (linear core member) made of a material having
a high elastic limit.
[0049] The mold 1 can be made of such metallic material as copper, copper alloy, sintered
hard metal or cemented carbide and may have disposed therein such a flow channel as
allow flow of a cooling medium or heating medium of fluid, gas, etc. The wire 3 may
have the surface coated with a film of TiO
2, TiN, TiC, etc. or may be made of such a material as spring steels, high tensile
strength steels, and superelastic materials, or the wire may be made of the material
having the above two characteristics in combination.
[0050] Incidentally, for the purpose of preventing the molten metal from forming an oxide
film, it is preferred to dispose the apparatus in its entirety in a vacuum or an atmosphere
of an inert gas such as Ar gas or establish a stream of an inert gas in the molten
metal injection region.
[0051] In the production of the cast article, a molten metal (not shown) is injected into
the cavity 2 of the mold 1 to cast a product. After the mold is cooled until the temperature
of the mold is lowered to a level of not more than the melting point of the molten
metal (not more than the glass transition temperature (Tg) in the case of an amorphous
alloy), the mold 1 is separated to allow extraction of the cast product 4 holding
the wire 3, as shown in Fig. 3B.
[0052] Thereafter, the wire 3 is drawn out from the resultant cast product to obtain the
cast article 4 having a small hole 5, as shown in Fig. 3C.
[0053] Fig. 4 illustrates an embodiment which uses the wire 3 coated with a surface film
6 of TiO
2, TiN, TiC, etc. mentioned above. By using the wire 3 preparatorily coated with such
surface film 6, when the wire is drawn, only the wire 3 can be drawn out from the
cast product 7 owing to the peeling of the surface film 6 from the wire 3, thereby
forming a small hole.
[0054] Fig. 5 illustrates another embodiment which uses the wire 3 made of a material having
a high elastic limit such as spring steels, high tensile strength steels, and superelastic
materials. By using the wire 3 made of the material having a high elastic limit, when
the wire is drawn, a slight gap is formed between the wire 3 and the cast product
7 because the wire itself deforms elastically. As a result, the wire 3 can be drawn
out from the cast product 7 so that a small hole is formed in the cast product.
[0055] Fig. 6 illustrates the schematic construction of another mode of embodying the apparatus
and method for the production of the cast article according to the present invention.
In Fig. 6, reference numeral 8 denotes a movable cylindrical guide member disposed
in the mold slidably so as to project into and draw back from the cavity 2 of the
mold 1. The wire 3 is set in the cavity 2 of the mold 1 together with the movable
cylindrical guide member 8 by inserting through a center bore of the guide member
8. By using such cylindrical guide member 8, a part of the wire 3 covered with the
guide member is protected from the contact with the molten metal and the surface area
of the wire being in contact with the cast product becomes small. As a result, the
proportion of the breakage of the wire 3 during the drawing step remarkably decreases.
[0056] Moreover, since a tension load is applied to the wire 3 in the longitudinal direction
thereof, the incidental bending of the wire 3 is effectively prevented even when the
molten metal flows into the cavity of the mold transversely in relation to the wire
3 or the turbulence of the molten metal occurs in the cavity of the mold. As a result,
a small hole may be formed in the cast article with high accuracy.
[0057] Fig. 7 shows the cast article 4a produced by using the apparatus shown in Fig. 6
mentioned above and the lower portion is severed from the cast article. The cast article
4a has a small diameter part 5a and a large diameter part 5b. The length of the large
diameter part 5b may be arbitrarily adjusted by changing the length of insertion of
the movable cylindrical guide member 8 into the cavity 2 of the mold 1. Incidentally,
the small diameter part 5a can be subjected to the wire lapping according to demand.
[0058] Although the elongated wire 3 having a uniform diameter in its overall length is
used in the embodiments mentioned above, it is also possible to use a wire (linear
core member) having a diameter increased stepwise or gradually in the direction of
drawing to form a small hole having the inside diameter increased stepwise or gradually
in its axial direction. Further, when the movable cylindrical guide member 8 as shown
in Fig. 6 is used, it is possible to form the small holes of various cross-sectional
shapes by using the guide members having varying cross-sectional shapes. Although
the above description was directed to the embodiments of the manufacture of cast articles
having a through-hole, it is also possible to manufacture a cast article having a
blind hole by adjusting the height of the linear core member to be set in the cavity
of the mold (insertion length).
[0059] According to the method and apparatus of the present invention, as mentioned above,
the problems caused by the difficulty of drawing of the linear core member from the
cast product after the casting or the durability of the core member is diminished
and a cast article having a small hole can be produced at low cost, with high productivity
and in a short time. As a result, the present invention allows a molded article satisfying
a predetermined shape, dimensional accuracy, and surface quality to be molded by a
simple process even when the article to be produced is an amorphous alloy molded article
having a slender hole and, therefore, enables to provide an inexpensive amorphous
alloy molded article having a small hole and excelling in the durability, mechanical
strength, resistance to impact and the like, particularly an optical connector part
such as a ferrule or capillary.
[0060] Now, the present invention will be described more concretely below with reference
to working examples which have confirmed the effect of the present invention specifically.
Example 1:
[0061] The casting was carried out by using an apparatus as shown in Fig. 3A and a wire
of stainless steel, 0.1 mm in diameter, having a coating of TiO
2, 10 µm in thickness, formed thereon by the PVD process. An alloy having a composition
of Zr
55Al
10Ni
5Cu
30 and previously manufactured by melting relevant component metals was subjected to
casting in a vacuum of 1.33 x 10
-2 Pa. A metal mold used had a cylindrical cavity, 2.5 mm in diameter and 10.5 mm in
length. After the casting, the cast product was extracted from the mold and the wire
was drawn out from the product at a speed of 1.7 mm/sec. to form a small hole. At
this step, the load for drawing was 294 N/mm
2. According to the observation of the formed hole with a microscope, it has confirmed
that the formed small hole had a circular cross-sectional shape of the stainless steel
wire.
Example 2:
[0062] The casting was carried out by using a metal mold similar to that used in Example
1 and a wire of titanium, 0.1 mm in diameter, having an oxide film of 5 µm thickness
formed on the surface thereof by oxidation. The load for drawing was 98 N/mm
2. According to the observation of the formed hole with a microscope, it has confirmed
that the formed small hole had a circular cross-sectional shape of the titanium wire.
Example 3:
[0063] The casting was carried out in the same manner as mentioned above by using a wire
of 45Ni-55Ti superelastic alloy, 0.1 mm in diameter, having an oxide film of 4 µm
thickness formed on the surface thereof. The load for drawing was 785 N/mm
2. According to the observation of the formed hole with a microscope, it has confirmed
that the formed small hole had a circular cross-sectional shape of the wire.
[0064] While certain specific embodiments and working examples have been disclosed herein,
the invention may be embodied in other specific forms without departing from the spirit
or essential characteristics thereof. For instance, the method explained above manufactures
one cast product by a single process using a metal mold provided with one molding
cavity. Naturally, the present invention can manufacture two or more cast products
by using a metal mold provided with two or more cavities therein. The present invention
is not limited to the embodiments mentioned above with respect to the size, shape,
and number of the cavities of the mold. Furthermore, the present invention is not
limited to the examples of application mentioned above. The described embodiments
and examples are therefore to be considered in all respects as illustrative and not
restrictive, the scope of the invention being indicated by the appended claims rather
than by the foregoing description and all changes which come within the meaning and
the range of equivalency of the claims are, therefore, intended to be embraced therein.
1. A method for the production of a cast article having a small hole, comprising the
steps of setting a linear core member of a desired cross-sectional shape in a cavity
of a metal mold, injecting a molten metal into the cavity of said metal mold to produce
a cast product, and drawing out said linear core member from the cast product to form
a small hole having the cross-sectional shape of the linear core member,
wherein a linear core member having a surface film formed by surface coating or by
subjecting to a surface treatment is used as said linear core member, and the linear
core member is drawn out from the cast product after the casting, thereby forming
in the cast product a small hole of the cross-sectional shape substantially equal
to that of the linear core member.
2. The method according to claim 1, wherein said linear core member is constructed so
that a part or the whole of said surface film is peeled off the surface of said linear
core member upon drawing the linear core member from the cast product after the casting,
thereby enabling the linear core member to be drawn from the inside of the cast product.
3. The method according to claim 1 or 2, wherein said surface film of said linear core
member is an oxide film, nitride film or carbide film containing a component element
of said linear core member.
4. The method according to any one of claims 1 to 3, wherein said linear core member
is made of a Ti-based alloy.
5. The method according to any one of claims 1 to 4, wherein said surface film of said
linear core member has a thickness in the range of 0.5 µm to 100 µm.
6. A method for the production of a cast article having a small hole, comprising the
steps of setting a linear core member of a desired cross-sectional shape in a cavity
of a metal mold, injecting a molten metal into the cavity of said mold to produce
a cast product, and drawing out said linear core member from the cast product to form
a small hole having the cross-sectional shape of the linear core member,
wherein said linear core member is so constructed as to elastically deform in the
drawing direction to have a diameter smaller than the original diameter upon drawing
the linear core member from the cast product after the casting, thereby enabling the
linear core member to be drawn from the inside of the cast product.
7. The method according to claim 6, wherein said linear core member is made of a Ni-Ti
superelastic alloy.
8. The method according to any one of claims 1 to 7, wherein said linear core member
has a diameter in the range of 0.025 mm to 1 mm.
9. The method according to any one of claims 1 to 8, wherein a tension load is applied
to said linear core member set in said mold in the drawing direction and in this state
the molten metal is injected into said cavity of the mold.
10. The method according to claim 9, wherein said tension load is not more than about
1960 N/mm2.
11. The method according to any one of claims 1 to 10, wherein said cast material is an
alloy containing an amorphous phase in a volumetric ratio of at least 50%.
12. The method according to claim 11, wherein said alloy is a substantially amorphous
alloy having a composition represented by either one of the following general formulas
(1) to (6):
M1aM2bLncM3dM4eM5f (1)
wherein M1 represents either or both of the two elements, Zr and Hf; M2 represents at least one element selected from the group consisting of Ni, Cu, Fe,
Co, Mn, Nb, Ti, V, Cr, Zn, Al, and Ga; Ln represents at least one element selected
from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm (mish metal:
aggregate of rare earth elements); M3 represents at least one element selected from the group consisting of Be, B, C, N,
and O; M4 represents at least one element selected from the group consisting of Ta, W, and
Mo; M5 represents at least one element selected from the group consisting of Au, Pt, Pd,
and Ag; and a, b, c, d, e, and f represent such atomic percentages as respectively
satisfy 25 ≦ a ≦ 85, 15 ≦ b ≦ 75, 0 ≦ c ≦ 30, 0 ≦ d ≦ 30, 0 ≦ e ≦ 15, and 0 ≦ f ≦15,
Al100-g-h-iLngM6hM3i (2)
wherein Ln represents at least one element selected from the group consisting of Y,
La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm; M6 represents at least one element selected from the group consisting of Ti, V, Cr,
Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W; M3 represents at least one element selected from the group consisting of Be, B, C, N,
and O; and g, h, and i represent such atomic percentages as respectively satisfy 30
≦ g ≦ 90, 0 < h ≦ 55, and 0 ≦ i ≦ 10,
Mg100-pM7p (3)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn,
and Zn; and p represents an atomic percentage falling in the range of 5 ≦ p ≦ 60,
Mg100-q-rM7qM8r (4)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn,
and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and
Ca; and q and r represent such atomic percentages as respectively satisfy 1 ≦ q ≦
35 and 1 ≦ r ≦ 25,
Mg100-q-sM7qM9s (5)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn,
and Zn; M9 represents at least one element selected from the group consisting of Y, La, Ce,
Nd, Sm, and Mm; and q and s represent such atomic percentages as respectively satisfy
1 ≦ q ≦ 35 and 3 ≦ s ≦ 25, and
Mg100-q-r-sM7qM8rM9s (6)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn,
and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and
Ca; M9 represents at least one element selected from the group consisting of Y, La, Ce,
Nd, Sm, and Mm; and q, r, and s represent such atomic percentages as respectively
satisfy 1 ≦ q ≦ 35, 1 ≦ r ≦ 25, and 3 ≦ s ≦ 25.
13. The method according to any one of claims 1 to 10, wherein said cast material is an
alloy for die casting selected from the group consisting of Al-based alloys, Mg-based
alloys, Zn-based alloys, Fe-based alloys, Cu-based alloys, and titanium alloys.
14. The method according to any one of claims 1 to 13, wherein said cast article is an
optical connector part for inserting or holding an optical fiber.
15. An apparatus for the production of a cast article having a small hole, comprising
a metal mold provided with a cavity which defines the outer shape of an article, a
movable cylindrical guide member having a center bore and disposed in said mold slidably
so as to project into and draw back from the cavity, and a linear core member to be
set in said-mold via the center bore of said cylindrical guide member.
16. The apparatus according to claim 15, further comprising means for applying a tension
load of not more than 1960 N/mm2 to said linear core member in its longitudinal direction.